Wingdrop while stalling

Hi,

there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Any help/advice/recollection of previous such problems and what you
did to fix it will be greatly appreciated.

Lars

drake wrote:
Hi,

there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally).

Sounds like a great trainer aircraft! If this problem common to the
type, or just this particular A/C?

The 50/50 part is interesting. Normally, if a plane is bent, it'll favor
one side or 'tuther.

Stall strips are a common way to improve stall performance, so as to
keep the tips flying (and ailerons working) while the root stalls. Does
the type have them?

Good luck...

nafod40 wrote in message ...
drake wrote:
Hi,

there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally).

Sounds like a great trainer aircraft! If this problem common to the
type, or just this particular A/C?

The 50/50 part is interesting. Normally, if a plane is bent, it'll favor
one side or 'tuther.

Stall strips are a common way to improve stall performance, so as to
keep the tips flying (and ailerons working) while the root stalls. Does
the type have them?

Good luck...

Some airplanes might have some nasty stall characteristics
caused by wing design, and sometimes such design is intentional to get
good aerobatic performance and to teach advanced flight maneuvers.
Most training airplanes are designed to have straightforward stalling
behaviour, some so forgiving that there is no real stall at all.
Newbie pilot students can get into big trouble real quick with stall
behaviour that drops one wing or the other.
Any certified airplane will have a straight-ahead stall break.
Wing drop is caused by one wing stalling slighty earlier, or the stall
on that side has progressed more than on the other, and if the wing
isn't out of rig, it's caused by uncoordinated flight. The nose of the
airplane isn't pointing straight ahead so that the airplane is sliding
slightly sideways as it stalls, and the wingtip that's farther aft
will stall first and drop. The same holds true for skidding turns; the
inside wing will drop first.
A power-on stall will most often drop the wing on the side that
has the upgoing prop blade; in North America, that's the left wing.
The rotating propwash strikes the wing root and causes a higher angle
of attack on that side, causing an earlier stall.

Dan

I once heard a neat story about stall spin characteristics.

It seems that a light airplane manufacturer wanted a piece of the two seat
training market that Cessna dominated with the C150/152. They designed and
built a nifty little low wing prototype that flew real nice with much better
performance than the 150/152 with the same power. Then they invited a bunch
of CFI's to fly it and asked, "How'd you like it?" "It doesn't spin - we
want to teach spins", they said.

The manufacturer hired some engineering consultants and said, "Make it
spin". The consultants added stall strips on the outboard wing to make the
wing tips stall first - and boy, did it spin. The manufacturer brought the
CFI's back and let them fly it again. The CFI's said, "Boy, does it spin".
"We like it", they said.

So, the manufacturer built some little airplanes and the CFI's and their
students started making smoking holes in the ground as they spun in.

"Wow", said the manufacturer, "we got to fix this". So, they hired another
bunch of aeronautical consultants who looked up "how to fix bad stall/spin
characteristics" in their "how to design little airplanes" book. The book
said, "add stall strips to the inboard wing", so that's what they did. Now
the little airplane would still spin, but not as enthusiastically as before.
With FOUR stall strips on the wing, it didn't perform worth a damn either.

Still, the manufacturer built a bunch of them before exiting the market.

Makes you wonder.

Bill Daniels

In article , drake says...

Hi,

there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Any help/advice/recollection of previous such problems and what you
did to fix it will be greatly appreciated.

Lars

Bet you don't have any wash out in the wings.If it was always the same wing then
it could be rigging. That's a starting point .

See ya

Chuck

drake wrote:

Hi,
there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Sounds like a good rudder trainer.

On Sat, 10 Jan 2004 00:03:57 GMT, john smith
wrote:

drake wrote:

Hi,
there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Sounds like a good rudder trainer.

Sounds like my Debonair. And...no it doesn't have wedges on the wing
roots although it does have the little 1/4 inch stall strips about 6
inches long. I don't think the first 60 or so had any washout either,
but I'd have to dig deeper on that.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Lars,
Fit wedges on the leading edges at the wing roots to force a root
stall. Some WW2 era military trainers tip stalled to enhance training
experience and the root wedge fix is used to remove the characteristic
(and surprise) for civilian warbird use.
Albert

(drake) wrote in message om...
Any help/advice/recollection of previous such problems and what you
did to fix it will be greatly appreciated.

Lars

Ditto Chuck's response. On one of my experimental gliders, I designed a
delta-wing using a reflex airfoil (M-178 I think.) However, I did not wash out
the tips, and I used wingtips that terminated in a sharp points. Big mistake.
When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.

Curiously enough, the Wright boys (yep, them again) used washed out wingtips on
the 1902 glider.

Harry "flies under polyethylene too" Frey

PS: Funny what you can learn from watching the (stress) hawks fly. Isn't it?

Wright1902Glider wrote:

When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.

Was this a model or was it piloted?

Dave 'bowling balls' Hyde